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. Author manuscript; available in PMC: 2014 Jun 23.
Published in final edited form as: J Neurosci. 1999 Sep 15;19(18):8152–8162. doi: 10.1523/JNEUROSCI.19-18-08152.1999

Figure 7.

Figure 7

Neuronal stimulation induces abnormal accumulation of extracellular K+ and burst discharge in post-FPI slices. Field electrode and KSM were placed in CA3 stratum radiatum. Stimulating electrode was placed in CA2 stratum radiatum. K+ activity recordings were performed during 0.05 and 1 Hz antidromic stimulation. A, Control slices ( filled circles) had a basal [K+]out similar to that of bathing aCSF. Antidromic stimulation at 1 Hz for 4 min induced a transient elevation of [K+]out to ~5 mm and its recovery toward baseline values within the fourth minute. During the following 0.05 Hz, [K+]out transiently decreased to ~4 mm and then recovered. Post-FPI slices (empty circles) had elevated basal [K+]out during stimulation at 0.05 Hz. When the high-frequency stimulation was performed [K+]out transiently increased to 5.4 mm and then decreased to 5 ± 0.05 mm without reaching the baseline value (asterisk; p < 0.001). During the following 0.05 Hz, [K+]out transiently decreased to ~4.7 mm. B, Post-FPI CA3 develops frequency-dependent afterdischarges for antidromic stimulation. In control, only a small fraction of slices developed afterdischarges during antidromic 1 Hz stimulation (28%; 2 of 7 slices). Post-FPI slices showed a higher excitability. They did not show afterdischarges during 0.05 Hz stimulation, but afterdischarges appeared during 1 Hz stimulation (80%; 8 of 10 slices). Two traces obtained at the end of a minute of 1 Hz-stimulation are showed overlapped.